Shares of Las Vegas Sands Corp were down more than 11 percent, MGM Mirage fell by about the same amount and Wynn Resorts fell 6.5 percent.

Portuguese news agency Lusa, quoting unnamed sources, reported on Tuesday that the Chinese government may tighten individual visas to Macau to one visit every six months from the current limit of one every two months.

"From the tone of the article and talking with our sources on the ground, we do not think the government has made a final decision yet," Morgan Stanley analyst Celeste Mellet Brown said in a research note.

She said the government has made it clear that it is determined to slow the strong gaming revenue growth seen in Macau and Morgan Stanley is forecasting year-over-year growth to drop from 50 percent in the first half of this year to around 25 percent in the second half and to 16 percent in 2009.

In July, China limited Macau visas under its individual visit scheme to once every two months. In addition, starting in September, mainland residents will no longer be able to enter Macau on a Hong Kong visa.

"The potential for China to continue to slow visitation (and hence gaming revenues) in Macau underscores a major risk of operating in this region," Lehman Brothers analyst Felicia Hendrix said in a research note.

Jefferies & Co analyst Larry Klatzkin cautioned that the potential limits have not been officially announced and he is hearing that the proposed restrictions would only be for Guangdong province.

"We are forecasting Macau gaming revenue growth of only 9.1 percent for the second half of 2008 and a decline of 8.3 percent in the first half of 2009," he said in a report.

Shares of Wynn fell $6.94, or 6.91 percent, to $93.45 on Nasdaq. MGM lost $3.50, or 11.18 percent, to trade at $27.80 and Sands dropped $5.93, or 11.64 percent, to $45.00, both on the New York Stock Exchange.